1. Field of the Invention
The present invention relates to tubular medical devices, and more particularly, to highly flexible, tubular medical devices such as catheters and guide wires having high initial torque transmission efficiencies.
2. Description of the Related Art
Intravascular catheters as well as other types of catheters are essential to the practice of modern interventional medicine. A catheter sheath introducer comprises three main components; namely a dilator, a cannula fitted with a hemostatic valve and a side port. Catheter sheath introducers allow guide wires and a variety of catheters to be safely introduced into the vasculature. There are many types of guide wires and catheters, including diagnostic catheters, guiding catheters, percutaneous transluminal angioplasty balloon catheters and self expanding stent delivery catheters. As stated herein there is a wide range of catheters that may be utilized in the vasculature or in virtually any other organ in the body that allows safe passage.
In a typical interventional arterial procedure, for example, stenting a stenotic region, a catheter sheath introducer is utilized to access a vessel that is of interest or will lead to the vessel of interest. Once access is achieved, a guide wire is inserted and moved through the vessel or vessels to the desired location, typically, distal to the treatment site. Once in position, various devices such as balloon catheters and balloon catheters with stents, may be introduced over the guide wire and moved into position at the desired location or treatment site.
U.S. Pat. No. 7,520,863 assigned to Cordis Corporation discloses a guide wire with a deflectable tip having improved torque characteristics. This patent illustrates the need to have a small diameter guide wire that includes a distal tip which may be deflected very precisely in either of two directions to enhance steerability. In particular, the guide wire comprises an elongated member formed with re-occurring steps, or step undulations, which is wound into a helical configuration so that adjacent turns can loosely interlock thereby preventing movement between adjacent turns. Such interlocking turns enhance the rotational rigidity or torquability of the coil such that when the proximal end of the coil is rotated, the distal end of the coil will eventually rotate also. Accordingly, the distal end of the coil more nearly tracks, rotationally, the proximal end of the coil.
In certain procedures, the vessel or vessels through which these elongated tubular devices have to be moved may be highly tortuous and/or highly angulated. Accordingly, the various devices that are inserted should preferably be flexible, steerable and pushable. These properties, as well as others, need to be balanced to create a device capable of traversing the most difficult pathways. In other words, it would be preferable to have a device that is flexible so that it may be steered through even the most tortuous pathway, but also rigid enough to be pushable to the desired location. In addition, physicians do not like a lack of high initial torque response. Basically, no physician engaging in an interventional procedure wants to make unnecessary movements. For example, when the physician wants to torque a guide wire in order to steer it, he or she wants an immediate response. More specifically, a cardiologist may be required to make a significant number of small or incremental position adjustments and thus desires to have a favorable tactile response from the device. In other words, it would be highly desirable that the device have a rapid torque response. Accordingly, there is a need for elongated tubular devices such as guide wires and catheters that have a high degree of flexibility, rigidity and torquability for steerage.